Roger Federer
's
worst enemy isn't his age. Or his balky back, at least at the moment. Or his small racket. Or the humidity. Or the fact that he was playing in Louis Armstrong Stadium for the first time since 2006.

His problem is simple, and it can be fixed, but it may take some time: Federer has, for a while now, forgotten how it feels to be Roger Federer.

At the U.S. Open on Monday, Federer, 32, turned in another distinctly un-Federer performance. He's making a habit of it, first with a quarterfinal defeat in Paris (hey, it happens, not a big deal); then a second-round loss at Wimbledon (that pretty much doesn't happen); then two upsets in Europe at small events to low-ranked players (worrisome); and now a 7-6(3), 6-3, 6-4 fourth-round loss at the U.S. Open to Tommy Robredo, a man Federer had beaten all 10 times they had played (gulp).

Robredo's upset ensured that the U.S. Open will not see its first-ever meeting between Federer and Rafael Nadal, who have played 31 times in their careers but never in New York. (Nadal won his fourth-round match later in the evening and will play Robredo on Wednesday.)

Federer had plenty of chances, none more important—and potentially transformational—than a 0-40 advantage on Robredo's serve in the fourth game of the third set. Given a chance to rile up the crowd and make Robredo wonder if he really had it in him to pull off this upset, Federer steadied himself, pressed ahead…and missed on four consecutive points. For the match, he converted two of 16 break points.

"I missed so many opportunities," Federer said afterward. "I kind of self destructed, which is very disappointing."

Federer has missed more than his share of opportunities for a while now. He hasn't won more than 30% of his return games in a season since 2006 (this year, he was at 26% headed into the Open, the same as he finished with last year). Federer used to be deadly in such moments: He would miss, he would frame a few shots, but eventually, he'd unleash a barrage of winners for a few games in a row and end a set.

"It doesn't take much with him," Andre Agassi said after Federer beat him in the 2005 U.S. Open final. "He can break a match open, or he can get back into it right away."

Against Robredo, Federer flirted with a break out…and then he pressed. He missed forehands early in rallies. He came to the net too late, or too soon. He served and volleyed on second serves. His strategy was at best suspect, at worst incoherent. Just last month, he had won a set off Nadal in Cincinnati and seemed to be, finally, on the upswing. The defeat against Robredo was nothing less than a crash, and he seemed to know it.

"That's not how I want to play from here on," Federer said. "I want to play better. I know I can. I showed it the last few weeks, that there is that level. So today was pretty frustrating."

For the first time since 2002, Federer will go an entire season without playing in a major final. He's now ranked No. 7, and it might be tough to gain much ground this fall. He has said previously that he'll likely test a new racket after the Open, as he did this summer.

What Federer needs most, though, is a bit of luck. No pain in his back for a long stretch. A few generous bounces on break points. A good draw. A super-sized dose of confidence.

"It takes care of all the things you don't usually think about," Federer said. "It's been a difficult last three months."

Before Federer was Federer—back in 2002, when he was the most talented underachiever in all of tennis—he looked something like he does now. Beautiful one moment, and then astonishingly bad, or even worse, indifferent, the next. He remembers those days well.

"People thought, 'Did he even try? Does he care much?'" he said. "The story of my life: When I lose, people are shell-shocked to see me play this way. If I win, it's the best thing."

People aren't as shocked as they once were, but it still doesn't feel right. It's too soon for that to be the real Roger Federer. Not yet.

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